The struggle to get changed without giving anyone a flash of ‘private’ flesh.

Crossing your arms to deny the very presence of those lumps which any minute now will make you want to die when you have to do some jumping jacks.

The pointless act of pulling down a too-short gym skirt.

And your shivering thighs which have turned to corned beef.

Is it any wonder girls will concoct excuses – “it’s me monthlies, sir, yes, for the third week in a row, sir” – to get out of this most humiliating lesson.

Boys have it easy. Puberty makes them leaner, taller and stronger whereas we go from whippets to hips overnight; it’s the equivalent of a Formula 1 racing car being souped up to look like Herbie when he went bananas.

Whether our physical changes do indeed slow us down or it’s all in the mind, it makes us withdraw – and it can last a lifetime.

Just look at Sport Wales’ School Sport Survey, which reveals boys are more likely to play sport than girls.

Girls’ participation in extra-curricular clubs is consistently lower than boys’.

Over time, girls’ interest wanes far more sharply than boys. Seventy-two per cent of male pupils and 71% of female pupils in primary school enjoy PE “a lot” compared with 62% of males and 40% of female pupils in secondary schools.

I refuse to believe these figures mean we lose the ability to love the buzz of running around, competition and getting sweaty. You only have to look at iconic heroines Tanni Grey-Thompson and Nicole Cooke for proof.

It is because we are conditioned to find those three things unfeminine.

The latest Sport Wales stats show only half of females play sport compared with two-thirds of males. Among the barriers are a lack of confidence and finding the prospect of joining in and being pitted against one another as daunting. What does this mean?

You have to look across the border to have it spelled out – after holding focus groups with women aged 14 to 40, Sport England found the overwhelming reason is because we fear being judged.

It doesn’t matter how old you are, it seems, jiggling boobs, being rubbish and puffing cheeks are as acutely embarrassing now for grown women as they are girls.

Back to Sport Wales and perception raises its head here too: research shows many women who take part in activities such as cycling, going to the gym and yoga do not consider themselves sporty. Yet I know men who consider they’re Gareth Bale because they once scored a goal against the Sully Colts in 1976.

Again, the men have it easy – brawn is good. But for women, bulk is bad. Sweat is manly, yet the only time you’ll see a woman being seen as desirable for a glistening body is if she’s advertising shower gel.

To change this, we need mums to show girls the benefits of sport. To smile when we perspire, as recommended by What Moves You?, the campaign to get women in Wales engaged in sport.

Schools need to rethink the PE kit – abandon shorts and skirts for lycra leggings, promote layers of breathable fabrics which look good and to make sports bras compulsory.

And how about the Welsh and UK Governments putting their money where their mouths are and fixing a deal with multinational sports brands to provide subsidised or sponsored PE kit? After all, aren’t they always asking us to move more and eat less because of the enormous social cost of obesity?

Of course, the media plays a role but it only gives us what we want – if we can change our perspective of what we consider to be desirable, then one day, I hope the next generation of girls will want to look healthy rather than half-starved and it will be those images we see.

Football fans get away with insulting female officials and the wives and girlfriends of players. Commentators go unpunished for making derogatory remarks about female competitors. Those at the top are immune too – the FA took no action over Premier League chief executive Richard Scudamore’s sexist emails.

If football can ban supporters from matches for racist chants, then why isn’t the same being done for sexism? Oh, I know: because there’d be empty terraces every single week.